What caused this??

[myxpykalix]

Or better yet....how do i fix it??

I have seen others have this problem but since it's never happened to me, i did'nt pay attention to the posts. It is not a problem with the bit slipping because other parts were done after this that were ok.

The board was held down good. The spoilboard was recently replaced and the plywood i cut just before this with the same bit was ok.

My thought was to just lower the bit by .10 (or ??) and rerun the same file? It was done with a .25 endmill

[Brian Harnett]

Looks to me the piece bowed up a little, I have this happen often to large glue up panels only secured at the edges. Vacuum hold down helps. I usually hand texture the background so its not an issue for me most of the time.

[gene]

I would say that the moisture content in the wood was a bit high. I had some trim do that . I let the wood dry out some more and that fixed it

[myxpykalix]

This was kiln dried cedar. It wasn't warped and if you look at the pics, it looks to me like it is a toolpath error. You see how it dug down in one pass to create the groove then moved back to it's normal height. The material was held flat and after carving did not bow or warp so it is not a materials issue.

I have seen others post similar pictures but i don't recall what, if any, their solutions was? Or if this is just one of those things where "gremlins got into the computer and maybe with another shallow pass i can get rid of it.

[bleeth]

How long since you serviced/replaced your pinions? Checked your motor mount adjustments? Went around and checked all bolts for tightness?

[steve_g]

“This was kiln dried cedar”
In my mind this is the # 1 culprit… I’ve had western KD Cedar shrink so much over night that cut letters no longer fit in their pockets! HD Cedar seems to have a lot of free moisture in it… just sorting through the rack you can tell the relative wetness by the weight difference!
My experience is that pocketing exposes the damper interior and hot router air blowing on it rapidly dries it out, causing dimensional changes.
The fact that the plywood you cut just before this project was ok, lends credence to my theory…
SG

[Chuck Keysor]

Jack, one way to easily tell if the blame is in the material, is to re-cut the piece in a piece of pink or blue Styrofoam. The material cuts beautifully and is cheap. If that cuts OK then of course you can blame your material with confidence. Chuck

[MogulTx]

If you do that, be sure to hold the center of the foam down with Double sided tape. This will keep it from moving around while getting machined.

[coryatjohn]

Another great medium to use for test cuts is machining wax. It's cheap, reusable and machines beautifully. There's no static and no need for dust collection as there is no dust. I love the stuff. Buy it in ten pound blocks and poor your own sheets with a cookie pan. Gather up the chips, melt them back down and poor another sheet. Also makes great mold material.

[garyr6]

Not my issue BUT I LIKE the wax idea.

[garyr6]

Where do you get yours?

[coryatjohn]

Oddly enough, this website: http://www.machinablewax.com/

[dlcw]

In my mind this is the # 1 culprit… I’ve had western KD Cedar shrink so much over night that cut letters no longer fit in their pockets! HD Cedar seems to have a lot of free moisture in it… just sorting through the rack you can tell the relative wetness by the weight difference!
My experience is that pocketing exposes the damper interior and hot router air blowing on it rapidly dries it out, causing dimensional changes.
The fact that the plywood you cut just before this project was ok, lends credence to my theory…
SG


I've had the exact same experience with KD cedar. Not the most stable of woods out there. On a long running (22 hours) I did a few years ago, I was amazed at how much the cedar changed dimensions as it was milled. It turned out ok but was interesting to be able to see the wood change dimensions like it did. On a long running project I did in hickory and alder, I did not have this dimension changing issue at all.